It is known from the literature that alpha-antimony oxide can be converted to beta-antimony oxide by heating the former to about 1130.degree. C. in dry oxygen. See for instance, "The Crystal Structure of Beta-Sb.sub.2 O.sub.4 : A New Polymorph", Proc. Chem. Soc., 400 (1964).
Catalysts comprising antimony and molybdenum and their use in oxidation reactions are well known from the following patents owned by the Assignee of record herein. U.S. Pat. No. 3,904,653, for instance, is directed toward the synthesis of maleic anhydride over a catalyst containing antimony and molybdenum, promoted by iron, vanadium or both.
U.S. Pat. No. 3,928,240 is directed toward a process of preparing catalysts containing molybdenum and oxygen with antimony, vanadium or tungsten. The process calls for partially reducing an aqueous solution or slurry of hexavalent molybdenum to a valence state below +6.
U.S. Pat. No. 4,021,427 is directed toward the oxidation of 1,3-butadiene to maleic anhydride with a catalyst containing molybdenum, antimony and vanadium with lithium or cerium or both and an optional reducing agent.
U.S. Pat. No. 4,065,468 discloses a process for the preparation of maleic anhydride from n-butane in the presence of a catalyst containing oxides of antimony, molybdenum and at least iron or vanadium with one or more optional promoter elements.
U.S. Pat. No. 4,240,931 is also directed toward the synthesis of maleic anhydride in the presence of an antimony/molybdenum oxide catalyst which contains at least one of niobium, zirconium, titanium and tantalum and an optional reducing agent.
As can be reasonably deduced from a review of the foregoing patents, antimony and molybdenum oxide containing catalysts can be promoted with a variety of elements and favorably used for the synthesis of maleic anhydride from a variety of compounds. Nevertheless, none of these patents discloses beta-antimony oxides, which can be prepared via a method of the present invention. Thus, the foregoing patents are only representative of the state of the art in antimony/molybdenum oxide catalysts.
It is also known that vanadium can be incorporated into antimony oxide at temperatures exceeding 800.degree. C. to form beta-Sb.sub.2 O.sub.4. These findings were reported in an article entitled "Investigations of Solid State Properties of Vanadium-Antimony Oxide Catalysts" J. of Catalysis 88, 236-236 (1984). Nevertheless, this work fails to teach that molybdenum could be substituted for vanadium.